The invention relates to a system and a method for producing a tangible three-dimensional object, such as a tangible model.
It is known in the field of Layered Manufacturing Technology (LMT)—often referred to as Rapid Prototyping (RP) or Rapid Manufacturing (RM)—to produce a tangible object. Rapid Prototyping (RP) and Rapid Manufacturing (RM), are called “Rapid” since they do not require a mould to be designed and manufactured.
An example of a LMT technique is the Stereo Lithography Apparatus (SLA). In SLA an object is produced by curing successive layers of a liquid resin in a suitable shape and size. The SLA includes a laser, which is used to cure a layer in the desired shape and size by moving the laser beam over the surface of a bath of photocurable resin. The movement of the beam over the surface is controlled to correspond to a CAD/CAM slice pattern of a designed 3D digital model of the object to be produced. Accordingly, the resin is cured in the shape of the respective slice pattern of the 3D digital model. After each curing step, the building platform supporting the object being produced is lowered, below the liquid level in the bath. The liquid resin will flow over the top surface of the object, forming a new resin layer. The new resin layer may then be cured corresponding to another CAD/CAM slice pattern.
However, a disadvantage of SLA is the long period of time required to produce the object. A reason for the low speed of the SLA is the fact that the laser has to “write” the slice patterns. Especially when large surfaces are required, this is relatively time consuming. Another shortcoming of the SLA is the long time for the resin surface to settle and straighten after lowering the object below the liquid level, and hence forming a new resin layer takes a relatively long time.
In the art of LMT, also an apparatus is known, sold by Envision Technologies GmbH, Germany under the name “Perfactory”, in which the disadvantages of the SLA are obviated. The apparatus employs, instead of a laser, a mercury lamp in combination with a micro-mirror array to project the desired slice pattern onto the surface of the photo-curable resin. Accordingly, a layer of resin is photo-cured more or less simultaneously, and hence faster than when writing a pattern with a laser beam.
The Perfactory further illuminates the resin bath from below, through a transparent glass plate covered with a transparent rubbery (silicone) anti-stick membrane. After curing, the glass plate is released from the freshly cured layer by means of automated pulling and liquid resin flows in the space between the glass plate and the freshly cured layer, thus forming the next layer to be cured. Accordingly, the resin layer is settled and straightened by the freshly cured layer and the glass plate when flowing into the space, and hence in a shorter time than in the SLA.
However, a common disadvantage of both the SLA and the Perfactory, is that it takes a relatively long period of time to produce the object. Typically, a cycle of producing a cured resin layer of about 25-150 micron takes about 15 to 40 seconds. Hence, already a small object of about 20 centimetres requires about 20 to 40 hours to be produced.